Gross leak detector and method

ABSTRACT

The invention contemplates observing the gross-leak condition of an article by immersing the same in a liquid inert to the material of the article. A chamber defines a limited volume surrounding the liquid and the article, and the chamber is evacuated while the article is immersed. As pressure reduces to a substantially evacuated condition, the immersed article is observed for the onset of telltale bubbles. The article is then promptly removed from the liquid while still at reduced pressure, thereby allowing the article to begin to dry immediately. The volume is then returned to ambient pressure as drying proceeds. Various specific refinements and embodiments are described.

[ Mar. 7, 1972 United States Patent Myers 3,114,257 12/1963 Fostereta1.............................73l45.5

[54] GROSS LEAK DETECTOR AND METHOD [72] Inventor:

Primary Examiner-Louis R. Prince Lester W. Myers, Seminole, Fla.

Assistant Examiner-William A. Henry, II Attorney-Sandoe, Hopgood &Calimat'de ABSTRACT The invention contemplates observing the gross-leakcondition of an article by immersing the same in a liquid inert to thematerial of the article. A chamber defines a limited volume surroundingthe liquid and the article, and the chamber is evacuated while thearticle is immersed. As pressure reduces to a substantially evacuatedcondition, the immersed article is observed for the onset of telltalebubbles. The article is then promptly removed from the liquid whilestill at reduced presthereby allowing the article to begin to dryimmediately. The volume is then returned to ambient pressure as dryingproceeds. Various specific refinements and embodiments are a u 7 r. H wa 3m m m e n m2, n 15 h smz 51 n m 3 n u J9 m .m m m m 5 m m WMMAM "3 P"m a m C m m m m mm m n m m D M W11 n P14 W5 m 9 w m w .L m w hm m n w st m FA Umfl 1 7 3 4H HUNG M U DD. UUUU l.

1,675,802 7/1928 Hamiltom. 2,567,215 9/1951 GROSS LEAK DETECTOR ANDMETHOD This invention relates to the detection of a leak condition in anarticle that is supposedly sealed against leakage.

The need exists for apparatus, particularly electrical apparatus, whichcan withstand great extremes of environmental operating conditions. Tomeet the need, components and circuits are being increasinglyminiaturized and sealed, but the question remains as to how effective isthe overall seal, upon fabrication and testing of the article. Differentmarkets have different needs of assurance as to the overall sealedintegrity of the article, and quality control is basic to the supply ofall these markets; an important difference in the ability to serve thesedifferent markets is the degree of ambient vacuum that can be assuredlywithstood without leakage.

Various devices and methods have been employed for gross-leak detectionin such articles. The military and space programs have perhaps the mostsevere requirements, and various official specifications have beenestablished, based on certain theories of leak detection and on certainapparatus in use today. In general, it can be stated that all presenttechniques and apparatus exhibit various disadvantages, among which canbe listed:

l. Extraordinary time consumption for each test, the time being in theorder of several hours per test, necessitating a statistical sampling ofproduction, rather than the testing of all components.

2. Leaks detected by liquid immersion have involved liquid contaminationof the article, meaning that it cannot be reworked but must be scrapped.

3. Undue handling of the article is involved.

4. Some of the tests require substantial pressure differentials and/or aheating cycle.

5. The time required has meant operator fatigue, with loss of testingeffectiveness and efficiency.

6. It has not been possible to achieve quantitative results, on aproduction basis.

It is an object of the invention to provide apparatus and a method whichsubstantially avoid the above-noted deficiencres.

Another object is to meet said object with a test cycle in the order ofone or a few minutes, rather than hours.

A further object is to meet the above objects within a maximum testpressure differential of 15 lbs./in. and without requiring heat, thusminimizing chances of article damage during the test.

A specific object is to obtain gross-leak data of the characterindicated, without contaminating or damaging the article, and permittingrework of the tested article, if necessary.

It is in general an object to meet the above objects with simpleapparatus, presenting minimum opportunity for article damage or operatorfatigue, and yielding positive qualitative and/or quantitative resultsas may be required, all with-a substantial economic saving, compared topresent techniques.

Another specific object is to meet the stated objects while achieving aleak sensitivity of at least substantially 1X10 cc./sec. of air.

Other objects and various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification in conjunction with the accompanyingdrawings. In said drawings, which show, for illustrative purposes only,preferred forms of the invention:

FIG. 1 is a simplified, partly schematic, vertical sectional viewthrough gross-leak detection apparatus of the invention;

FIGS. 2, 3 and 4 are reduced, further simplified similar diagrams toillustrate different relationships in a cycle of use of the apparatus ofFIG. 1;

FIGS. 5 and 6 are simplified similar diagrams to illustrate twosuccessive modifications;

FIG. 7 is a simplified fragmentary sectional view of a modification ofpart of FIG. 1; and

FIG. 8 is a schematic diagram, partly in vertical section, to showadditional component apparatus in use with structure otherwise as inFIG. 1.

Briefly stated, the invention contemplates observing the gross-leakcondition of an article by immersing the same in a liquid inert to thematerial of the article. A chamber defines a limited volume surroundingthe liquid and the article, and the chamber is evacuated while thearticle is immersed. As pressure reduces to a substantially evacuatedcondition, the immersed article is observed for the onset of telltalebubbles. The article is then promptly removed from the liquid whilestill at reduced pressure, thereby allowing the article to begin to dryimmediately. The volume is then returned to ambient pressure as dryingproceeds. Various specific refinements and embodiments are described.

FIG. 1 illustrates the invention in a system in which an article to betested is suspended from a beam 11. Beam 11 is rocked to immerse article10 in liquid 12 within a suitable vessel, shown as a glass beaker 13.All operations are performed within an enclosing chamber, whichconveniently comprises a glass bell jar 14 having sealing engagement atits base rim 15 against a substantial flat base (plate) or table 16.Various fluid connections 17-18-19 through the baseplate 16 enableevacuating, beam-actuating, and refilling functions within the chamberenclosure.

In accordance with a feature of the invention, the vacuum, availablefrom a suitable supply such as a pump (now shown), serves the dualfunctions of evacuating the chamber and of actuating beam 1 l for liquidimmersion of the article 10. And in analogous fashion, the inert gassupply for refilling the chamber serves the added function ofwithdrawing the article 10 from liquid 12 at the outset of the refillingprocess. These respective supply connections are shown with theirindividual shutoff valves or petcocks 20-21.

Upstanding structure fixed at flange 22 to the base plate 16 carries anarm 23 to provide a horizontal axis fulcrum for beam 11. As shown, arm23 has a bifurcated upper end, with a knife edge crotch 24 to define thefulcrum. Serrations 25 along the underside of beam 1! permitfulcrum-position selection, as appropriate to the actuating stroke toaccommodate articles 10 of different size. The upstanding framestructure includes a cylinder 26, cylinder head 27 and block 28, forsupporting the fulcrum arm 23 and for guided alignment of the stem 29 ofa piston 30. Piston is shown with peripheral groove containing a sealring 31, although a metal-backed fiber piston has also been found to besatisfactory. A link 32 connects the end of stem 29 to the end of beam25, to eliminate angularity effects.

For the form shown, the fluid connection 17 serves a conduit 33communicating exclusively with cylinder 26 in the space above the piston30. The fluid connection 18 serves another conduit 34 which ispreferably sufficiently rigid to be self-supporting and yet sufficientlysoft to adapt to such bending as may be needed to selectively adjust theorientation of a nozzle 35; conduit 34 may be of soft copper tubing, andnozzle 35 is used to direct inert drying gas at the article 10, once itis removed from the liquid 12, and throughout the drying andchamber-filling phase. The fluid connection 19 is an exhaust port forthe chamber 14-16, and a check valve 36 to the vacuum pump line assuresits exclusive use for this purpose. Conveniently, a pressure indicator37, such as a manometer, is connected between check valve 36 andconnection 19, to track the evacuated pressure status within thechamber.

The remaining fluid-pressure connections are dominated by a two-wayselector valve 40 which is manipulated to selectively connect either thevacuum supply line 41 or the inert gas supply line 42 to the interior ofthe chamber. In FIG. 1, valve 40 is in its EVACUATE" position, whereingas line 42 is blocked and wherein the vacuum line 41 serves separatebranches 43-44 to the base connections 17-18. A throttle 45 in line 43enables adjustment of the rate of actuating beam 11, depending on thesize and weight of article 10, and depending on the fulcrum selectionalong serrations 25. A petcock 46 in line 44 enables sequencing, asdesired, of beam actuation in relation to commencement of evacuation ofthe substantial remaining volume in the enclosing chamber. Upon shiftingvalve 40 to its F ILL" position, the vacuum line 41 is blocked, and theinert gas supply line 42 admits drying gas both to retract the beam andits suspended article and to direct a mild blast of drying flow at theretracted article.

In the sequence of FIGS. 2, 3 and 4, the apparatus is first shown withjar 14 removed, in order that article may first be suspended, invertical register with the immersion liquid 12. Conveniently, for thecase of the integrated circuit shown as the test article 10, analligator clip 47 grips one bank of leads of article 10, and preferablythe suspension line from clip 47 to the end of beam 11 includes a freelyswiveling element 48, such as a swivel link commonly used by anglers forlure connections; element 48 establishes a vertical swivel axis. Thebeam 11 is in its raised position, being thus held by the dominatingmoment attributable to piston 30 and its connections to beam 11, itbeing noted that beam 11 achieved this position at the close of the testcycle for the previous article 10, with piston 30 in its down position.Before setting the jar 14 in place, to close the chamber, theorientation of nozzle 35 is checked to make sure it will direct dryinggas at article 10; the axis of such direction is preferably generallytransverse to but slightly offset from the swivel axis of element 48 sothat when supplied with drying gas, the nozzle discharge will spinarticle 10 and thus enhance drying action.

FIG. 3 illustrates the relation of parts after jar 14 has been appliedtoclose the chamber, and after valve 40 has been shifted to its EVACUATEposition. This at once actuated beam 11 to immerse the article 10 inliquid 12. Evacuation proceeds, and an observant watch is kept for thefirst sign of bubbles escaping from the article 10. When such bubblesappear, the operator reads the pressure indicator 37 and shifts valve 40to its FILL position, whereupon gas admitted in line 33 is operative toreturn piston 30 to its down position and at the same time to withdrawarticle 10 from the liquid (FIG. 4). This withdrawal occurs whileevacuated conditions exist, and so there is no opportunity for liquid 12to be induced to flow into any crevice that may have been responsiblefor the detected leak. Moreover, the nozzle discharge and articlespinning are such as to extract virtually all liquid entrained uponwithdrawal; so that drying is virtually complete by the time the inertgas has returned the chamber pressure to ambient. The latter conditionis recognized by a gentle intermittent jogging of the jar 14 as it mustslightly rise to relieve gas forced into the chamber, the gas pressurebeing regulated to a level slightly above ambient, e.g., to 16 lbs./in.

FIGS. 5 and 6 illustrate alternative structures for accomplishingarticle immersion and withdrawal. In FIG. 5, the article 50 is held atfixed elevation throughout the test cycle, while the vessel (beaker) 51is raised and lowered for the respective immersion and withdrawalfunctions. The fluidpressure-operated means 52 includes a stem linked toa beam 53, supported by a pivot pin connection to the standard 54 whichprovides article suspension; the alternating vacuum and gas connectionsto means 52 are beneath its piston, so that a vacuum drops the piston topull down the left end of beam 53, and so that the piston and associatedend of beam 53 are raised during the gas-fill phase of the cycle. Thebeaker-51 is cradled in a yoke or collar 55 having gimbal-pivotconnection at 56 to the forked end of beam 53. For convenience inmounting the. article 50, it is suspended from an arm 57 pivoted tostandard 54; its lower position is shown in full lines, resting at alocating stop or bracket 58. In the raised arm position 57 (dashedoutline), article 50 is clear of the beaker 51. Finally, anozzle-supporting conduit 59 is poised to direct drying gas at article50 upon liquid withdrawal, at commencement of gas filling, and whilevacuum conditions exist; it will be noted that by off-axis introductionof .drying gas into the limited volume of beaker 51 and above its liquidlevel, the swirling gas may more effectively induce article spinning.The cycle is otherwise as described for FIGS. 1 to 4.

In FIG. 6, neither the article 60 nor the vessel 61 (for im mersionliquid) is moved during the test cycle. On the other hand, the liquid ispositively withdrawn and returned, by the action of reciprocatingpositive displacement pump means 62, having a fluid-communicatingconduit connection 63 to the lower part of vessel 61. Fluid-pressuremeans 64, similar to that at 26-30-33 in FIG. 1, may oscillate a beam 65to operate the pump 62. The article 60 may be suspended as in FIG. 5,and therefore corresponding parts are given the same reference numbers.Again, a nozzle conduit 66 is set for swirling discharge at and aroundthe article 60, when pump 62 retracts liquid from vessel 61 and, hence,also from article 60.

FIG. 7 represents a modification wherein a single fluid-communicatingconnection 67 through the baseplate 68 serves all actuating, evacuating,filling and drying functions within the sealed chamber and throughoutthe test cycle. Connection 67 is directly served by the two-way selectorvalve 40, and the indicator 37 is connected therebetween, to monitorchamber pressure. Within the chamber, the nozzle conduit 69 is mountedto connection 67. A check valve branch line 70 permits evacuationunlimited by nozzle restrictions, and further assures that allgas-filling will proceed via the nozzle discharge or upper end ofconduit 69. An opening 71 at the upper end of cylinder 72 is largecompared to that of bleed connection at the lower end of cylinder 72.The relative sizes of these openings is such as to establish actuatingpressure differentials across piston 74, with each shift of position atvalve 40. Thus, for the vacuum-selected position shown, the bleed 73 hasso restricted the outgassing of volume under piston 74 (compared to themuch more prompt outgassing of volume above piston 74) that piston 74 isdriven up, to the position shown, to accomplish article immersion as inFIG. 1. To hold this actuated position, the beam 75 must first have beenbalanced, as by counterweight means 76, so that by the time the volumebeneath piston 74 is evacuated to substantially the extent of all therest of the chamber 14, the article immersion position will hold. Havingdetected a leak, or having otherwise conducted the test to the necessaryextent, valve 40 is reversed to supply drying gas to fill the chamber.Again, the bleed restriction 73 causes piston 74 to respondpreferentially to gas admitted at port 71, thereby immediatelywithdrawing the article for drying, as previously described. Thiswithdrawn position, with piston 74 in its down position, will be held,since no further actuating pressure difference can develop across piston74, until valve 40 is again shifted. Adjustments are shown for the bleed73 and for counterweight 76, to accommodate particular balance andaction responses which apply for articles 10 of different size andweight.

FIG. 8 is a fragmentary diagram devoted to the automatic accomplishmentof some of the described operations. In particular, the vessel whichcontains the immersion liquid 12 is constructed to become anondistorting part of a bubble-detecting optical system, schematicallyarrayed on the axis 81. As shown, spaced vertical walls 82-83 of vessel80 are optically flat, and axis 81 passes horizontally through liquid 12in the region above the immersed test article 10. Collimating lenses84-85 span the walls 82-83 and establish a collimatedlight volume (inliquid 12) through which bubbles 86 must rise, if they should occur;thus, bubbles 86 will disturb the collimated nature of light betweenlenses 84-85.

To detect such disturbance, lenses 84-85 are shown imaging a diaphragmslit 87 on a stop 88. A light source 89 utilizes a lens 90 to illuminatethe diaphragm 87, and a lens 91 directs light passing the stop 88 tophotoelectric means 92. Normally, the illuminated region in the liquidwill remain collimated, so that light will focus upon and therefore notpass the stop 88. However, the onset of bubbles 86 will destroy orimpair the collimated nature of the light, resulting in passage of lightto the photoelectric means 92. Amplifier means 93 serving the Thus, theoutput of processor 95 may operate an alarm or indicator, to alert theoperator to a bubble condition.

Specifically, the output of processor 95 may be one of the coordinateinputs to a display device or recorder 96. The other input 97 to displaymeans 96 reflects instantaneous chamber pressure, and the electricalline 97 will be understood schematically to suggest the output of asuitable pressure-tracking transducer forming part of the indicator 37.Thus, display means 96 may include means for digital or other readout ofinstantaneous chamber pressure (i.e., vacuum condition), and the outputof processor 95 may be a pulse to synchronize, gate or trigger thereadout or recording of such instantaneous pressure.

As a further feature, an actuator 98 for valve 40 may also electricallyrespond to a bubble-indicating output from processor 95. Thus, valve 40may be automatically shifted to its FILL position, as soon as a bubblecondition is detected.

FIG. 8 also serves to show that in certain situations it may not benecessary or desirable to rely upon bubble detection, before drying thetest article and refilling the chamber. For example, if the gross-leaktest requirement for the particular article should be exceeded (i.e., agiven reduced pressure or vacuum condition met) without bubblegeneration, then there is no need to proceed with further reduction inpressure. In such case, a threshold device 99, connected to thepressure-indicative line 97 and to the valve actuator 98, may initiatethe reversing shift of valve 40, upon achievement of a thresholdindicative of the specified test minimum of chamber pressure. A furthercontrol connection of threshold means 99 to the display means 96provides displayed confirmation of the achievement of the said minimumpressure condition.

The described method and apparatus will be seen to achieve theabove-stated objects. Operation is basically simple and relatively fast.In use with the presently preferred inert fluorocarbon liquid 12,namely, a 3M-Company product designated FC-43, the complete test cycleis performed in approximately 3 minutes, with instances of test times inthe order of 1 minute; this is to be compared with the approximately 4-hour period involved in other test techniques using pressurized andheated fluorocarbons. In my technique, there is no heating, and themaximum test-pressure differential is p.s.i., as compared with thepotentially damaging 100 p.s.i. of the other techniques. In mytechnique, 1 have found that no liquid is drawn into a leaky" article,and that the article is not in any way damaged by the test cycle, thusenabling rework of the article after test.

The liquid FC-43 has been found the best of all liquids that I have thusfar tested. It is characterized by the relatively high density of about116 lbs/ft. at room temperature (72 F.); it also has the greatestviscosity, lowest vapor-pressure, and highest boiling point of suchinert liquids as l have considered. Specifically, this liquid has notbeen found, in my test procedure, to exhibit the phenomenon ofnucleation, i.e., gas bubble formation on minute rough surfaces of thetest article, so that leak bubble observation is positive, clear andunobstructed.

As preliminary precaution, l commence each day's use of the apparatus bydegassing the indicating liquid 12 for 15 minutes, for which period thepressure level indicator 37 displays a vacuum of at least 29.5 inchesHg. Thus readied, my equipment exhibits an air-leak sensitivity of 1X10cc./sec.; it has actually crossed over this lower limit of gross-leakdetection and exhibits sensitivity at the upper end of the region offine-leak detection, i.e., in the range of 1X10 cc./sec.

The foregoing quantitative information is developed by noting, at 37,the pressure at which bubbles commence, it being recalled that pressureis steadily declining until the bubbles appear. The noted pressure ischecked against a precalibrated chart, to the leakage rate to which thisbubble-onset pressure corresponds. l have generated the calibrationchart by using a Veeco Mass Spectrometer Leak Detector, Model M812,modified with an extra-large roughing pump and an unchoked 85liters/sec. diffusion pump (to increase speed) so as not to To do this,the electron multiplier gain was reduced and emission current set to 2ma.

It will be appreciated that the description of the invention hasconcerned itself primarily with coaction of mechanical and opticalparts, and that, for simplicity, the showings have been somewhatschematic to eliminate detail not necessary to the claimed invention.For example, it will be understood that contrast-enhancing techniquesmay be employed to visually accentuate the onset of bubbles in theliquid 12. When the vessel 13 is a beaker, such enhancement is easilyachieved by locally adhering to the outer wall of the beaker a piece ofblack nonreflecting paper, as by pressure-sensitive tape, in the regionwhich is the background against which bubbles are to be observed.

While the invention has been described in detail for preferred methodsand forms, modifications may be made without departure from the scope ofthe invention. Thus, the actuating means for displacing the arm 11 maybe strictly mechanical, through suitable sealing means (such as abellows) in the base 16, rather than pressure-operated (as shown), andof course such mechanical movements may involve longitudinaldisplacement or rotary displacement, or both, as will be understood.

What is claimed is:

1. The method of inspecting the overall integrity of seal effectivenessin a sealed article by observing its gross-leak condition, whichcomprises immersing the article in a liquid inert to the material of thearticle, evacuating a selected limited volume surrounding the liquid andimmersed article, observing the reduced pressure at which leak bubblesbegin to escape from the article, removing the article from liquidcontact while still at reduced pressure, whereby the article can beginto dry immediately, and then returning said volume to the ambientpressure external to said volume.

2. The method of claim 1, in which the liquid is contained in an openreservoir within said volume, and in which the article is lowered forimmersion and is raised for drying.

3. The method of claim 2, in which the article is agitated to acceleratedrying.

4. The method of claim 3, in which the return to ambient pressure isaccomplished by introducing an inert gas into said volume, and in whichsaid agitation results from the localized and directional introductionof said gas.

5. The method of claim 3, in which agitation includes spinning thearticle on a vertical axis.

6. The method of claim 5, in which the return to ambient pressure isaccomplished by introducing an inert gas into said volume, and in whichsaid introduction is so localized and directed at the article afterremoval from the liquid as to spin the same.

7. The method of claim 1, in which the return to ambient pressure isaccomplished by introducing an inert gas into said volume.

8. The method of claim 1, in which the liquid is cyclically displaceablefrom a relation of removal from article contact to a relation of articleimmersion, and return, all within said volume.

9. The method of gross-leak inspecting a sealed article, which comprisesimmersing the article in a fluorocarbon liquid, evacuating a selectedlimited volume surrounding the liquid and immersed article, the limitingdegree of vacuum being that prescribed for the test, observing theliquid for leakrevealing bubbles escaping from the article, removing thearticle from liquid contact while still at reduced pressure, whereby thearticle can begin to dry immediately, and then introducing an inertdrying gas into said volume to return the same to ambient pressure.

10. The method of claim 9, in which said liquid is a fluorocarbon ofrelatively high density.

11. The method of claim 9, in which said gas is nitrogen.

l2. Gross-leak-testing apparatus, comprising a selectivelyopenablechamber, first means for containing a supply of liquid within saidchamber, second means for supporting an article to be gross-leakevaluated in said chamber, fluid-pressure-operated displacement meanswithin said chamber for relatively displacing said first and secondmeans to selectively effect article immersion in and article-freedomfrom liquid in said first means, a vacuum connection to said chamber, agas supply connection to said chamber, said connections including meansfor opening and closing the same, said displacement means being soconnected for fluid-pressure response as to effect article-immersingdisplacement in response to evacuation of said chamber and to effectreverse displacement to free the article from liquid immersion uponsupply of gas to said chamber, and means coordinating the interlacedoperation of said connections, whereby upon commencement of evacuationthe article may be liquid-immersed and may remain immersed until saidlast-mentioned means is operated to remove the article from the liquidupon commencement of restoration of pressure within said chamber, sothat the article can be drying throughout the period in which pressurein said chamber is being restored to ambient.

13. Apparatus according to claim 12, in which said chamber and saidfirst means include transparent walls to permit viewing an immersedarticle under evacuated conditions.

14. Apparatus according to claim 12, in which one of said first andsecond means includes a beam fulcrummed on a horizontal axis in saidchamber, said displacement means being connected in actuating relationwith one end of said beam, and means at the other end of said beam andpoised in vertical register with the other of said first and secondmeans.

15. Apparatus according to claim 12, in which said second means includesa beam fulcrummed on a horizontal axis in said chamber, saiddisplacement means being connected in actuating relation with one end ofsaid beam, and article-suspen sion means at the other end of said beamand poised in vertical register with said means for liquid containment.

16. Apparatus according to claim 12, in which said first means includesa beam fulcrummed on a horizontal axis in said chamber, saiddisplacement means being connected in actuating relation with one end ofsaid beam. and liquid container support means at the other end of saidbeam and poised in register beneath said article-supporting means.

17. Apparatus according to claim 12, in which said second means includesmeans for positioning the article within the container of said firstmeans, and in which said displacement means includes means forselectively displacing liquid into and out of said first means, foreffecting selective liquid immersion of the article.

18. Apparatus according to claim 14, in which said beam includes meansfor selectively positioned fulcrum support, whereby for a given strokeof said displacement means, the stroke of article-to-liquid relativedisplacement can be varied to accommodate article size.

19. Apparatus according to claim 12, in which said articlesupport meansincludes an article suspension freely rotatable on a vertical axis.

20. Apparatus according to claim 12, in which a discharge nozzle isconnected to said gas supply connection and is directed at the region ofarticle positioning when said displacement means is in the position forwhich the article is free of the liquid immersion relationship.

2|. Apparatus according to claim 20, in which said articlesupport meansincludes an article suspension freely rotatable on a vertical axis, andin which said nozzle is directed on an axis offset from said verticalaxis.

22. Apparatus according to claim 12, and including a bubble-presencedetector comprising an optical system with a light source andphotoelectric means effectively positioned below the liquid surface andabove the immersed location of the supported article, display meansincluding a pressureresponsive device connected to track evacuationpressures in said chamber, and a display-operating connection from saidphotoelectric means to said display means for automaticall displaying anindication of the evacuation pressure at who bubble presence isdetected.

23. Apparatus according to claim 22, and second displayoperating meansincluding threshold-operated means in the connection to saidpressure-responsive device to determine a second display upon tracking athreshold of minimum evacuation pressure, whereby it can be indicatedthat the article has achieved such threshold without exhibiting leakage.

24. Gross-leak detection apparatus, comprising a chamber, first meansfor evacuating said chamber, second means including inert gas supplymeans for returning said chamber to ambient pressure, control means forsequentially connecting said first and second means to said chamber, avessel within said chamber and containing an inert high-density liquid,anarticle-support mechanism within said chamber and means coordinatedwith said control means for bringing the article and the liquid into andout of immersed relation, pressure-responsive means for monitoringinstantaneous chamber pressure, bubble-presence-detecting meansresponsive to the onset of a bubble condition within the liquid, andrecording means responsive to both said two last-defined means forrecording the pressure at which bubbles are first detected.

25. Gross-leak detection apparatus, comprising a chamber, first meansfor evacuating said chamber, second means including inert gas supplymeans for returning said chamber to ambient pressure, control means forsequentially connecting said first and second means to said chamber, avessel within said chamber and containing an inert high-densityliquid,an article-support mechanism within said chamber and means coordinatedwith said control means for bringing the article and the liquid into andout of immersed relation, pressure-responsive means for monitoringinstantaneous'chamber pressure, bubble-presence-detecting meansresponsive to the onset of a bubble condition within the liquid, and acontrol connection from said bubble-presence-detecting means to saidcontrol means and operative to shift the connection of said chamber fromsaid first means to said second means upon detection of a bubblecondition.

26. The apparatus of claim 25, in which said pressureresponsive meansincludes a threshold-operated signal generator for producing an outputsignal upon achievement of a predetermining' minimum test pressure, saidsignal generator being also connected to said control connection,whereby said chamber and article will be automatically returned toambient pressure if said minimum test pressure is reached withoutdetection of bubbles.

1. The method of inspecting the overall integrity of seal effectivenessin a sealed article by observing its gross-leak condition, whichcomprises immersing the article in a liquid inert to the material of thearticle, evacuating a selected limited volume surrounding the liquid andimmersed article, observing the reduced pressure at which leak bubblesbegin to escape from the article, removing the article from liquidcontact while still at reduced pressure, whereby the article can beginto dry immediately, and then returning said volume to the ambientpressure external to said volume.
 2. The method of claim 1, in which theliquid is contained in an open reservoir within said volume, and inwhich the article is lowered for immersion and is raised for drying. 3.The method of claim 2, in which the article is agitated to acceleratedrying.
 4. The method of claim 3, in which the return to ambientpressure is accomplished by introducing an inert gas into said volume,and in which said agitation results from the localized and directionalintroduction of said gas.
 5. The method of claim 3, in which agitationincludes spinning the article on a vertical axis.
 6. The method of claim5, in which the return to ambient pressure is accomplished byintroducing an inert gas into said volume, and in which saidintroduction is so localized and directed at the article after removalfrom the liquid as to spin the same.
 7. The method of claim 1, in whichthe return to ambient pressure is accomplished by introducing an inertgas into said volume.
 8. The method of claim 1, in which the liquid iscyclically displaceable from a relation of removal from article contactto a relation of article immersion, and return, all within said volume.9. The method of gross-leak inspecting a sealed article, which comprisesimmersing the article in a fluorocarbon liquid, evacuating a selectedlimited volume surrounding the liquid and immersed article, the limitingdegree of vacuum being that prescribed for the test, observing theliquid for leak-revealing bubbles escaping from the article, removingthe article from liquid contact while still at reduced pressure, wherebythe article can begin to dry immediately, and then introducing an inertdrying gas into said volume to return the same to ambient pressure. 10.The method of claim 9, in which said liquid is a fluorocarbon ofrelatively high density.
 11. The method of claim 9, in which said gas isnitrogen.
 12. Gross-leak-testing apparatus, comprising a selectivelyopenable chamber, first means for containing a supply of liquid withinsaid chamber, second means for supporting an article to be gross-leakevaluated in said chamber, fluid-pressure-operated displacement meanswithin said chamber for relatively displacing said first and secondmeans to selectively effect article immersion in and article-freedomfrom liquid in said first means, a vacuum connection to said chamber, agas supply connection to said chamber, said connections including meansfor opening and closing the same, said displacement means being soconnected for fluid-pressure response as to effect article-immersingdisplacement in response to evacuation of said chamber and to effectreverse displacement to free the article from liquid immersion uponsupply of gas to said chamber, and means coordinating the interlacedoperation of said connections, whereby upon commencement of evacuationthe article may be liquid-immersed and may remain immersed until saidlast-mentioned means is operated to remove the article from the liquidupon commencement of restoration of pressure withIn said chamber, sothat the article can be drying throughout the period in which pressurein said chamber is being restored to ambient.
 13. Apparatus according toclaim 12, in which said chamber and said first means include transparentwalls to permit viewing an immersed article under evacuated conditions.14. Apparatus according to claim 12, in which one of said first andsecond means includes a beam fulcrummed on a horizontal axis in saidchamber, said displacement means being connected in actuating relationwith one end of said beam, and means at the other end of said beam andpoised in vertical register with the other of said first and secondmeans.
 15. Apparatus according to claim 12, in which said second meansincludes a beam fulcrummed on a horizontal axis in said chamber, saiddisplacement means being connected in actuating relation with one end ofsaid beam, and article-suspension means at the other end of said beamand poised in vertical register with said means for liquid containment.16. Apparatus according to claim 12, in which said first means includesa beam fulcrummed on a horizontal axis in said chamber, saiddisplacement means being connected in actuating relation with one end ofsaid beam, and liquid container support means at the other end of saidbeam and poised in register beneath said article-supporting means. 17.Apparatus according to claim 12, in which said second means includesmeans for positioning the article within the container of said firstmeans, and in which said displacement means includes means forselectively displacing liquid into and out of said first means, foreffecting selective liquid immersion of the article.
 18. Apparatusaccording to claim 14, in which said beam includes means for selectivelypositioned fulcrum support, whereby for a given stroke of saiddisplacement means, the stroke of article-to-liquid relativedisplacement can be varied to accommodate article size.
 19. Apparatusaccording to claim 12, in which said article-support means includes anarticle suspension freely rotatable on a vertical axis.
 20. Apparatusaccording to claim 12, in which a discharge nozzle is connected to saidgas supply connection and is directed at the region of articlepositioning when said displacement means is in the position for whichthe article is free of the liquid immersion relationship.
 21. Apparatusaccording to claim 20, in which said article-support means includes anarticle suspension freely rotatable on a vertical axis, and in whichsaid nozzle is directed on an axis offset from said vertical axis. 22.Apparatus according to claim 12, and including a bubble-presencedetector comprising an optical system with a light source andphotoelectric means effectively positioned below the liquid surface andabove the immersed location of the supported article, display meansincluding a pressure-responsive device connected to track evacuationpressures in said chamber, and a display-operating connection from saidphotoelectric means to said display means for automatically displayingan indication of the evacuation pressure at which bubble presence isdetected.
 23. Apparatus according to claim 22, and seconddisplay-operating means including threshold-operated means in theconnection to said pressure-responsive device to determine a seconddisplay upon tracking a threshold of minimum evacuation pressure,whereby it can be indicated that the article has achieved such thresholdwithout exhibiting leakage.
 24. Gross-leak detection apparatus,comprising a chamber, first means for evacuating said chamber, secondmeans including inert gas supply means for returning said chamber toambient pressure, control means for sequentially connecting said firstand second means to said chamber, a vessel within said chamber andcontaining an inert high-density liquid, an article-support mechanismwithin said chamber and means coordinated with said control means forbringing the article and the liquid into and out of immersed Relation,pressure-responsive means for monitoring instantaneous chamber pressure,bubble-presence-detecting means responsive to the onset of a bubblecondition within the liquid, and recording means responsive to both saidtwo last-defined means for recording the pressure at which bubbles arefirst detected.
 25. Gross-leak detection apparatus, comprising achamber, first means for evacuating said chamber, second means includinginert gas supply means for returning said chamber to ambient pressure,control means for sequentially connecting said first and second means tosaid chamber, a vessel within said chamber and containing an inerthigh-density liquid, an article-support mechanism within said chamberand means coordinated with said control means for bringing the articleand the liquid into and out of immersed relation, pressure-responsivemeans for monitoring instantaneous chamber pressure,bubble-presence-detecting means responsive to the onset of a bubblecondition within the liquid, and a control connection from saidbubble-presence-detecting means to said control means and operative toshift the connection of said chamber from said first means to saidsecond means upon detection of a bubble condition.
 26. The apparatus ofclaim 25, in which said pressure-responsive means includes athreshold-operated signal generator for producing an output signal uponachievement of a predetermining minimum test pressure, said signalgenerator being also connected to said control connection, whereby saidchamber and article will be automatically returned to ambient pressureif said minimum test pressure is reached without detection of bubbles.